Pico Parking Sensor

parking_sensor.py

from machine import Pin
from utime import sleep_us, ticks_us, sleep

trig=Pin(17, Pin.OUT)
echo=Pin(16, Pin.IN)
buzzer=Pin(27, Pin.OUT)

buzzer.value(1)
sleep(0.5)
buzzer.value(0)

def calc_cm(echo, trig):
    ## a 10 us signal to trig starts the internal ranging program of the sensor.
    trig.low()
    sleep_us(2)
    trig.high()
    sleep_us(10)
    trig.low()
    ## echo pin is set high when the first pulses are sent out, so wait for the echo to go high
    while echo.value() == 0:
        pass
    ## Now record the time, then wait until the echo pin goes low, which means the echo has been received.
    t1 = ticks_us()
    while echo.value() == 1:
        pass
    # Record the time again, as the echo has been received
    t2 = ticks_us()
    ## Calulate time difference.
    ## Speed of sound is approx 340m/s, which is 0.034 cm/us
    ## But the sound has traveled twice the distance, so need to / 2
    ## s = t * v
    ## s = (t2-t1) * 0.034 / 2
    ## s = (t2-t1) * 0.017 which is approximately
    cm = (t2 - t1) / 58.0
    return cm

while True: 
    cm = calc_cm(echo, trig)
    print(cm)
    if cm < 60:
        buzzer.value(1)
        sleep(0.01 * cm)
        buzzer.value(0)
        sleep(0.01 * cm)